Cardiopulmonary distress is the major cause of death in the neonatal period. Generally the approach to management has been similar to that in the adult and has included methods to increase cardiac output. Recently we have shown that oxygen consumption per kg of weight increases dramatically after birth and is parallelled by a marked increase in cardiac output. Within 10 weeks there is a marked reduction in oxygen consumption and cardiac output in relation to body weight. In view of the high resting cardiac output required to provide oxygen to the tissues, there is very little reserve in response to stress. We propose to consider therapy of circulatory failure in the newborn lamb by attempting to decrease oxygen requirements by 1) sedation with meperidine, chlorpromazine and promethazine; 2) muscle relaxants; 3) assisted ventilation; 4) general anesthesia. These observations will be made in normal lambs and in animals subjected to various types of circulatory stress such as hypoxia, hemorrhage, left-to-right shunts and increased right and left ventricular afterload.